The provision of mass market Internet services presents traffic management problems for both telecommunications carriers and Internet Service Providers.
At present most private users are connected to the Internet over modems which operate in the voice band. These services have low transmission rates and also tie up the exchange connection preventing simultaneous use of the phone on the same line and loading the exchange.
High speed access technologies have emerged which make the delivery of fast data and data-like services practical for the mass/broad market. Such technologies include transmission technologies such as ADS and Hybrid Fibre Coax and multiplexing/Switching technologies such as ATM
A number of IP based access services have been implemented and often use ATM. as an underlying transport technique. However in these implementations, the carriage of services must be based on the Internet Protocol by necessity and so the underlying ATM flows must be terminated at each location at which IP traffic is processed. Therefore in IP based access networks which use ATM as the underlying transport, the advantages of using end to end ATM are foregone.
For an ATM end to end based access service, it has been necessary to establish individual ATM connections carrying AAL5 encapsulated data across the entire network between each subscriber and their ISP(s) of choice. In a mass market deployment of ATM technology, for example high speed Internet access based on ATM to residential subscribers, the number of ATM flows can amount to 10s to 100s of thousands simultaneously.
A service provided, such as an Internet Service Provider, may need to terminate an individual information flow from each to its subscribers. This requirement could be imposed for service reasons, billing reasons, security reasons or routing reasons. Typical large ISPs must design their systems to cope with up to hundreds of thousands of subscribers.
In an ATM connected scenario, at least two issues arise for service providers:
ATM interface cards for switches and workstations terminate a finite maximum number of simultaneous ATM connections. Typically, this maximum number of connections is of the order of 1000 or fewer. This maximum number of ATM connections is significantly fewer than the number of subscribers to a large ISP. PA1 The cost of leased public ATM links is generally relatively expensive compared with the competitive price charged for a single residential internet service. In order to remain viable, ISPs offering high speed internet access over ATM would therefore require each leased ATM link into the public network to be shared by a relatively large number of residential subscribers. Certainly, the number of subscribers sharing a 155 Mbit/s link (for example) would need to be much greater than 1000.
Routing in the access network via traditional means is unsuitable in a multi service provider environment or in an environment where the service provider is different from the access network provider. This is because "routing" is a service which provides a value added connectivity and could potentially lead to traffic nominally service by a particular service provider to bypass or be routed around that service provider altogether.
Other issues arise in an ATM connected scenario which affect both access carriers and service providers:
The logistical and technical difficulty of managing individual end to end ATM connections for each subscriber is significant.